Ok so I have a motor in a sedan that was sat for years
I adjusted the valves as they were all tight I've driven it maybe 300 miles it's now smokey uneven but when driving seems to go ok
And appears to only smokes at idle

I swapped out some injectors which made it a bit better but how often after not being adjusted should I re adjust the valves?

I have read that this condition could be knocking off the carbon so they will need adjusting again allready but... should I drive it hard for more miles first or add anything to fuel or oil?
Can I fit new stem seals without pulling it to pieces?
Thanks